Actuatable loadport system

ABSTRACT

A system adapted to exchange wafer carriers between an overhead transport mechanism and a platform is provided. The system employs a wafer carrier having at least one handle extending therefrom, an overhead transfer mechanism, a transporter coupled to the overhead transfer mechanism and adapted to move therealong and having a wafer carrier coupling mechanism adapted to couple to the at least one wafer carrier handle, a platform positioned below the overhead transfer mechanism such that wafer carriers traveling along the overhead transfer mechanism travel over the platform, and an actuator coupled to the platform and adapted so as to elevate the platform to an elevation wherein the loading platform may contact the bottom of a wafer carrier coupled to the overhead transfer mechanism.

[0001] This application is a continuation of U.S. patent application Ser. No. 09/755,394 filed Jan. 5, 2001, which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to fabrication systems and more particularly to an improved method and apparatus for loading and unloading wafer carriers to and from a tool.

BACKGROUND OF THE INVENTION

[0003] A factory for manufacturing semiconductor substrates (e.g., patterned or unpatterned wafers) is conventionally known as a “FAB.” Within a FAB, an overhead transport mechanism may transport semiconductor wafers in what is known as a wafer carrier (e.g., a sealed pod, a cassette, a container, etc.) between various processing systems, wherein a wafer carrier is placed on a mechanism known as a loadport (i.e., a mechanism or location which receives and supports a wafer carrier at a given tool). Certain loadports referred to herein as fabrication tool loadports, support a wafer carrier while wafers are extracted from the wafer carrier and transported into a processing system coupled thereto. Others simply receive a wafer carrier within a storage buffer, where the wafer carrier is stored for subsequent transport to a fabrication tool loadport.

[0004] Typically, wafer carriers are received in a storage buffer via an elevated or overhead loadport that receives wafer carriers from an overhead transport mechanism. Thereafter a storage buffer robot may transfer the wafer carrier from the overhead loadport to another storage shelf or to a fabrication tool loadport or to a conventional SEMI Standard E15 loadport that exchanges wafer carriers with an overhead transport mechanism. To lower the wafer carrier from an overhead transport mechanism to an overhead loadport, a robot capable of multi-axis movement may be employed, etc. The complex multi-axis movement required by such a loader robot in order to transfer a wafer carrier between the overhead transfer mechanism and the overhead loadport increases equipment expense and reduces equipment reliability.

[0005] Also, conventionally wafer carriers have kinematic mounts (i.e., mechanical couplings used to align a wafer carrier on a platform, such as a loadport), which engage corresponding kinematic mount locations on a loadport. Thus, the loader robot must be tightly toleranced to accurately position the wafer carrier on the loadport such that the wafer carrier's kinematic mounts may engage the loadport's kinematic mount locations. Such tight tolerance requirements may increase equipment costs while reducing equipment throughput.

[0006] Accordingly, there is a need for an improved system that may transfer wafer carriers between an overhead transport mechanism and a loadport.

SUMMARY OF THE INVENTION

[0007] The present invention provides a system adapted to exchange wafer carriers between an overhead transport mechanism and a platform. The system employs a wafer carrier having at least one handle extending therefrom, an overhead transfer mechanism, a transporter coupled to the overhead transfer mechanism and adapted to move therealong and having a wafer carrier coupling mechanism adapted to couple to the at least one wafer carrier handle, a platform positioned below the overhead transfer mechanism such that wafer carriers traveling along the overhead transfer mechanism travel over the platform, and an actuator coupled to the platform and adapted so as to elevate the platform to an elevation wherein the loading platform may contact the bottom of a wafer carrier coupled to the overhead transfer mechanism.

[0008] The invention further comprises a method of transferring wafer carriers between an overhead transport mechanism and a platform, by elevating the platform so as to contact a wafer carrier supported by the overhead transport mechanism, and so as to release the wafer carrier from the overhead transport mechanism. Thereafter the platform is lowered to an overhead loadport height.

[0009] An inventive wafer carrier comprising at least a first handle comprising a groove, such as an inverted “v-shaped” groove, along a lower surface thereof, is further provided.

[0010] Other features and aspects of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a side schematic view, in pertinent part, of an overhead transport system and an inventive loadport for use therewith;

[0012]FIG. 2 is a front perspective view of the wafer carrier having a conventional bar-type handle attached thereto, shown coupled to an overhead transporter;

[0013]FIG. 3 is a front perspective view of a wafer carrier having an inventive V-shaped handle attached thereto, shown coupled to an overhead transporter;

[0014] FIGS. 4A-D are schematic side plan views of the overhead transport system and the inventive loadport system;

[0015] FIGS. 5A-D respectively are the front plan views that correspond to the side views of FIGS. 4A-D;

[0016]FIG. 6 is a side view of a storage apparatus that may comprise the loading platform; and

[0017]FIG. 7 is a schematic top plan view, in pertinent part, of an overhead transport system coupled to a processing system useful in describing exemplary locations where the inventive loadport may be employed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018]FIG. 1 is a side schematic view, in pertinent part, of an inventive overhead transport system 11 that comprises an inventive loadport 12, having a lift actuator 13 that may elevate a platform 15) to an elevation wherein the platform 15 may contact a wafer carrier 17 (e.g., a sealed pod, an open cassette, etc.) being transported by an overhead transport mechanism 19 (e.g., an overhead conveyor). The inventive overhead transport system 11 may further comprise the wafer carrier 17, the overhead transport mechanism 19, a plurality of transporters 21 adapted to move along the overhead transport mechanism 19. The inventive overhead transport system 11 may also comprise alignment marks or sensors 51 and 53 (FIGS. 4A-5D) adapted to transmit a signal when the wafer carrier 17 is in a predetermined position relative to the loading platform 15.

[0019] The operation of the inventive overhead transport system 11 is further described below with reference to FIGS. 4A-D and FIGS. 5A-D, which illustrate the inventive overhead transport system 11 in more detail than that shown in FIG. 1. Before discussing the overall operation of the inventive overhead transport system 11, it is best to understand the configuration of the exemplary types of wafer carriers that may be employed therewith. Specifically, the opposing sides of the wafer carrier 17 may have a twist-on location (e.g., a threaded or Bayonette extension) such that a handle (e.g., having corresponding threads or wings) may be removably coupled to the twist-on location. The twist-on location 35 (FIGS. 2 and 3) may be positioned at the wafer carrier 17's center of gravity so as to minimize vibration of the water carrier 17 while the wafer carrier 17 is being transported by the overhead transfer mechanism 19. Two types of handles may be used with the wafer carrier 17. The first type of handle may comprise a conventional bar as described further below with reference to FIG. 2, and the second type of handle may comprise an inventive inverted V-shaped handle as described further below with reference to FIG. 3.

[0020]FIG. 2 is a front perspective view of a wafer carrier 17 having a conventional bar-type handle 26 attached thereto, shown coupled to the transporter 21 a. The transporter 21 a may comprise a pair of grippers 27 adapted to be positioned on opposing sides of the wafer carrier 17, and a coupling mechanism 29 adapted to couple the transporter 21 a to the overhead transfer mechanism 19 and to allow the transporter 21 a to move therealong as is conventionally known. In one aspect, the grippers 27 have no moving components (i.e., are fixed). Specifically, the grippers 27 extend downwardly from the coupling mechanism 29, and the distance between the grippers 27 is larger than the width of the wafer carrier 17. The grippers 27 may comprise an end effector 31 adapted to couple to the conventional bar-type handle 26. As shown in FIG. 2, the end effector 31 may have a groove 33 that has, for example, a V-shape (as shown), a U-shape (not shown), or any other similar shape which may “grasp”, cradle or otherwise engage the conventional bar-type handle 26 from below. The twist-on location 35 (FIGS. 2 and 3) may be positioned at the wafer carrier 17's center of gravity so as to minimize vibration of the wafer carrier 17 while the wafer carrier 17 is being manually transported or is being transported by the overhead transfer mechanism 19.

[0021] The transporter 21 a may further comprise a rocking restraint 37 such as a pair of rigid extensions that extend downwardly from the coupling mechanism 29 to a position close to the top of the wafer carrier 17, and are thus adapted to minimize rocking (e.g., forward and backward) of the wafer carrier 17 as the wafer carrier 17 is being transported by the overhead transfer mechanism 19.

[0022]FIG. 3 is a front perspective view of the wafer carrier 17 having an inventive V-shaped handle 41 attached thereto, shown coupled to the transporter 21 b. The transporter 21 b may comprise the same components as the transporter 21 a of FIG. 2. In this aspect, however, the end effector 31 may comprise a rod 43 that is adapted to couple to the V-shaped handle 41 of the wafer carrier 17. As previously described, the inventive V-shaped handle 41 may comprise a threaded region that may be screwed onto a threaded region of the twist-on location 35. In operation, the groove 33 of the inventive V-shaped handle 41 may “grasp”, cradle or otherwise engage the rod 43 of the transporter 21 b, such that the transporter 21 b may be lifted and lowered thereby.

[0023] The components of the inventive overhead transport system 11 are described further with joint reference to FIGS. 4A-5D, which are useful in describing the operation of the inventive overhead transport system 11, as a wafer carrier 17 is transferred between the overhead transport mechanism 19 and the loading platform 15. FIGS. 4A-D are schematic side plan views of the inventive overhead transport system 11, and FIGS. 5A-D are the respective front plan views of the inventive overhead transport system 11 that correspond to FIGS. 4A-4D.

[0024] Generally, in operation, a transporter 21 carries a wafer carrier 17 into position above the inventive loadport 17. The inventive loadport 17 then elevates such that the handles 41 of the wafer carrier 17 disengage the transporter's end effectors. The transporter then moves forward and the inventive loadport is able to lower the wafer carrier to a position from which the wafer carrier 17 can be extracted and loaded to a fabrication tool. To accomplish such wafer carrier transfer between an overhead transporter and a fabrication tool, the lift actuator 13 is coupled to the platform 15 so as to elevate the platform 15 to an elevation wherein the platform 15 may contact the bottom of a wafer carrier 17 being transported by the overhead transfer mechanism 19. The lift actuator 13 may lift and lower the platform 15 between various positions including: (1) an upper position in which the platform 15 has elevated the wafer carrier 17 such that the handle thereof is above the level of the transporter 21 a, 21 b's end effector 33 thus lifting the wafer carrier 17 off of the transporter 21; and (2) a lower position in which the platform 15 has lowered the wafer carrier 17 so that a robot 45, 65 (FIGS. 6 and 7) may access the wafer carrier 17.

[0025] In order to avoid collision, the distance between the top of a wafer carrier 17 supported by the platform 15 and the overhead transport mechanism 19 is larger than the distance between the overhead transport mechanism 19 and the bottom of a wafer carrier 17 being transported thereby (the distance being measured when the platform 15 is in the lower position). Thus, the wafer carrier 17 may not contact the overhead transport mechanism 19 or any overhead portion of the transporter 21 a, 21 b when the loading platform 15 is in the upper position (assuming the wafer carrier 17 is disengaged form the rods). Also, the distance between the top of the wafer carrier 17 and the rocking restraint 37 measured before the platform 15 contacts the wafer carrier 17, is larger than the distance between the top of the wafer carrier 17 and the rocking restraint 37 measured when the loading platform 15 is in the upper position. Thus, the wafer carrier 17 may not contact the rocking restraint 37 when the loading platform 15 is in the upper position, unless the wafer carrier 17 rocks forward or backward.

[0026] The platform 15 may be positioned below the overhead transport mechanism 19 such that a wafer carrier 17 that is being transported by the overhead transport mechanism 19 may travel over the loading platform 15. In one aspect, the platform 15 may be a top shelf of a storage apparatus (e.g., a local buffer) that may comprise a plurality of shelves and one or more loadports as described further below with reference to FIG. 6.

[0027] The alignment sensors may comprise a light transmitter 51, such as a light emitting diode (LED) and a receiver 53, such as a photodetector. A microcontroller 55 may be coupled to the lift actuator 13 and adapted to control the operation thereof. The microcontroller 55 may be further adapted to receive a signal from the receiver 53 indicating the wafer carrier 17 is in position above the platform 15. Specifically, in one aspect, the alignment sensors 25 may employ the use of a “through-beam” technique whereby the light transmitter 51 is positioned so as to transmit a light beam to the receiver 53 “through” a path traveled by a wafer carrier 17 as it travels along the overhead transfer mechanism 19. The light transmitter 51 may be positioned on the platform 15 and the receiver 53 may be positioned on the overhead transfer mechanism 19.

[0028] When a wafer carrier 17 being transported by the overhead transport mechanism 19 is above the loading platform 15, the wafer carrier 17 may block a beam of light that is transmitted by the transmitter 51. When a wafer carrier 17 is not above the loading platform 15, the receiver 53 may detect a beam of light that is transmitted by the light transmitter 51 (i.e., the beam of light may pass through). An output of the receiver 53 may have a “first signal” value when the beam of light contacts the receiver 53, and may have a “second signal” when the beam of light does not contact the receiver 53. As a further precaution, the lift actuator 13 may lift and lower the platform 15 only when the microcontroller 55 receives a “second signal” from the receiver 53.

[0029] The operation of the inventive overhead transport system 11, employing the transporter 21 b of FIG. 3 (with the wafer carrier 17 having the inventive V-shaped handle 41 attached thereto) is described with reference to the sequential views of FIGS. 4A-D and FIGS. 5A-D, which show the movement of the wafer carrier 17 as the wafer carrier 17 travels between the overhead transfer mechanism 19 and the platform 15.

[0030]FIGS. 4A and 5A show the wafer carrier 17 coupled to the transporter 21 b, and the wafer carrier 17 positioned above the platform 15. The platform 15 is shown in the retracted position prior to contacting the wafer carrier 17. The receiver 53 outputs a “second signal” because the beam of light transmitted by the light transmitter 51 is blocked by the wafer carrier 17. The microcontroller 55 receives the second signal from the receiver 53, and actuates the lift actuator 13.

[0031] Upon actuation, the lift actuator 13 elevates the platform 15 to the upper position, wherein the platform 15 contacts and elevates the wafer carrier 17 such that the bottom of the inventive V-shaped handle 41 is above the level of the rod 43, thus lifting the wafer carrier 17 off of the transporter 21 b. As shown in FIGS. 4B and 5B, the platform 15 is in the upper position and the wafer carrier 17 is positioned thereon. Once the platform 15 is in the upper position and because the inventive V-shaped handle 41 is above the level of the rod 43, the transporter 21 b may then move along the overhead transport mechanism 19, as shown in FIGS. 4C and 5C. Thereafter, the lift actuator 13 retracts carrying the platform 15, to the lower position, wherein the robot 45 may access the wafer carrier 17, as shown in FIGS. 4D and 5D. The robot 45 may then transfer the wafer carrier 17 to a storage shelf (FIG. 6) below the platform 15 or to the processing apparatus 63 (FIG. 7).

[0032] After all the wafers have been processed in the wafer carrier 17, the inventive overhead transport system 11 may reverse the steps described above, to thereby return the wafer carrier 17 to the overhead transport mechanism 19 for transport to another processing tool. Because the inventive transport system may employ only linear motion, wafer carrier loading and unloading may be more efficient. In one aspect, the overall transfer time may be about 5 to 10 seconds for the wafer carrier 17 to travel between the platform 15 (e.g., when configured as an overhead loadport) and the overhead transport mechanism 19.

[0033] When the inventive overhead transport system 11 employs the transporter 21 a of FIG. 2 so as to transport a wafer carrier 17 having a conventional bar 26 attached thereto, the operation is similar to that described above. Upon actuation, the lift actuator 13 elevates the platform 15 to the upper position, wherein the conventional bar 26 is above the top of the V-shaped groove 33 of the transporter's end effector 31 a (rather than the V-shaped handle being above the bar shaped end effector 31 as shown in FIG. 3). Thus, the wafer carrier 17 is lifted off of the transporter 21 a.

[0034]FIG. 6 is a side view of a storage apparatus 57 that may comprise the loading platform 15. As stated above, the storage apparatus 57 may comprise a plurality of shelves 59 and a plurality of loadports 61 positioned below the shelves 59 and adjacent a processing system 63 (FIG. 7). In one aspect, the shelves 59 are within the footprint of (e.g., above or below) the loadports 61. The storage apparatus 57 may also comprise a robot 45, which may transfer the wafer carrier 17 between the shelves 59 and the loadports 61 a-e. As shown, the loadports 61 a-b are overhead loadports, for receiving a wafer carrier from an overhead transport mechanism, and the loadport 61 c is a SEMI standard E15 loadport which conventionally receives wafer carriers either manually or from a robot. Because a clear path exists between the loadports 61 a-c these loadports may advantageously be configured in accordance with the invention so as to include an actuator as previously described. Similarly the loadports 61 d-e, if positioned in front of the shelves 59 rather than below them (e.g., positioned outside the footprint of the shelves 59), may also be configured in accordance with the invention. Accordingly, with use of the present invention a loadport positioned for manual loading at a height set by SEMI Standard E15 may also receive wafer carriers from an overhead transport mechanism. A specific aspect of the storage apparatus 57 is described in detail in U.S. patent Ser. No. 09/201,737, the entire disclosure of which is incorporated herein by this reference.

[0035]FIG. 7 is a schematic top plan view, in pertinent part, of a processing system 63 having a factory interface wafer handler 65 adapted to transport wafers between the plurality of loadports 61 c-e and a processing tool 67, which may comprise a plurality of processing chambers 69. FIG. 7 shows exemplary positions in which the inventive loadports 61 a-e may be employed.

[0036] As is evident from the description above, the inventive overhead transport system 11 may reduce equipment expense and increase equipment reliability. The inventive overhead transport system 11 may allow for loose wafer carrier positioning tolerance when robots are not employed, as wafer carriers need not be positioned as accurately.

[0037] It will be understood that, depending on the configuration of the inventive loadport, situations may arise where a wafer carrier being transported by an overhead transport mechanism will need to travel past an overhead loadport that has a wafer carrier positioned thereon. To avoid enough, and the actuator can have a long enough stroke so that there is sufficient vertical space for both wafer carriers. Alternatively the inventive loadport may have a cantilever extension (not shown) on the platform so that a wafer carrier can be temporarily extended out of the path of the overhead transport mechanism. A further alternative configuration may employ a rotatable platform as shown and described with reference to FIG. 8.

[0038]FIG. 8 is a schematic top plan view of an inventive transport system that employs a rotatable platform 81 having the inventive loadport 12 (of FIG. 1) mounted thereon. Accordingly, the rotatable platform may be installed below an overhead transport mechanism 19 such that the inventive loadport 12 may be rotated to a position below the overhead transport mechanism 19 such that wafer carriers may be exchanged between the inventive loadport 12 and the overhead transport mechanism 19. After receiving a wafer carrier 17 from the overhead transport mechanism 19, the rotatable platform may rotate to position the wafer carrier 17 at a location where a fabrication tool robot may extract the wafer carrier (e.g., the location shown in phantom).

[0039] In the specific aspect shown in FIG. 8, the rotatable platform 81 may be employed within the storage apparatus 57 of FIG. 6 (e.g., the rotatable platform 81 may be employed within the inventive loadport 61 b of FIG. 6). In such an aspect, the storage apparatus's robot 47 would move along track 83 (FIG. 6) in order to transport wafer carriers between the inventive loadport (when the rotatable platform 81 is in the location shown in phantom) and the plurality of storage shelves 59 (FIG. 6). Accordingly, the aspect shown in FIG. 8 may be employed within a fabrication system such as that described in a U.S. patent application Ser. No. 09/517,227, filed Mar. 2, 2000 titled “FABRICATION SYSTEM WITH EXTENSIBLE EQUIPMENT SETS”, the entire disclosure of which is incorporated herein by reference.

[0040] The foregoing description discloses only the exemplary embodiments of the invention, modifications of the above-disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the transporter 21 may support the wafer carrier 17 via a hook-shaped end effector that couples to the flange positioned on top of a conventional wafer carrier 17. The V-shaped groove 33 may be replaced by any other similar shape.

[0041] Accordingly, while the present invention has been disclosed in connection with the preferred embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims. 

The invention claimed is:
 1. A method of exchanging wafer carriers between an overhead transport mechanism and a local storage apparatus, the method comprising: positioning a frame of a storage apparatus that comprises a plurality of storage shelves such that the storage is adjacent an overhead transport mechanism adapted to support and transport wafer carriers; positioning a movable portion of the storage apparatus in vertical alignment with a position through which a first wafer carrier supported by the overhead transport mechanism will travel; moving the movable portion of the storage apparatus vertically toward the first wafer carrier; contacting the first wafer carrier with the movable portion of the storage apparatus; and moving the first wafer carrier relative to the overhead transport mechanism via the contact with the movable portion of the storage apparatus such that the movable portion of the storage apparatus supports the first wafer carrier and the overhead transport mechanism no longer supports the first wafer carrier.
 2. The method of claim 1, wherein positioning a movable portion of the storage apparatus in vertical alignment with a position through which a first wafer carrier supported by the overhead transport mechanism will travel comprises positioning the movable portion of the storage apparatus below the position through which the first wafer carrier will travel.
 3. The method of claim 1, wherein moving the movable portion of the storage apparatus vertically toward the position through which a first wafer carrier will travel comprises elevating the movable portion.
 4. The method of claim 1, wherein contacting the first wafer carrier with the movable portion of the storage apparatus comprises causing the first wafer carrier to locate atop the movable portion.
 5. The method of claim 5, wherein the step of causing the first wafer carrier to locate atop the movable portion occurs before the step of moving the first wafer carrier relative to the overhead transport mechanism via the contact with the moveable portion.
 6. The method of claim 1, wherein contacting the first wafer carrier with the movable portion of the storage apparatus comprises achieving kinematic coupling between the movable portion and the first wafer carrier.
 7. The method of claim 1, wherein moving the first wafer carrier relative to the overhead transport mechanism comprises elevating the first wafer carrier relative to the overhead transport mechanism.
 8. The method of claim 7, wherein elevating the first wafer carrier off of the overhead transport mechanism comprises elevating the first wafer carrier off of a wafer carrier support of the overhead transport mechanism.
 9. The method of claim 8, wherein moving the first wafer carrier relative to the overhead transport mechanism further comprises lowering the first wafer carrier relative to the overhead transport mechanism.
 10. The method of claim 7, wherein moving the first wafer carrier relative to the overhead transport mechanism further comprises lowering the first wafer carrier relative to the overhead transport mechanism.
 11. The method of claim 10, further comprising causing horizontal relative motion between the first wafer carrier and the wafer carrier support to prevent contact between the first wafer carrier and the wafer carrier support during lowering the first wafer carrier relative to the overhead transport mechanism.
 12. The method of claim 1, wherein moving the first wafer carrier relative to the overhead transport mechanism comprises lowering the first wafer carrier relative to the overhead transport mechanism.
 13. The method of claim 12, wherein moving the first wafer carrier relative to the overhead transport mechanism further comprises elevating the first wafer carrier relative to the overhead transport mechanism before lowering the first wafer carrier relative to the overhead transport mechanism.
 14. The method of claim 1, further comprising lowering the first wafer carrier to a location of a load port.
 15. The method of claim 14, wherein lowering the first wafer carrier to a location of a load port comprises lowering the first wafer carrier to a load port of the storage apparatus supported by the frame of the storage apparatus.
 16. The method of claim 1, further comprising delivering the first wafer carrier to a shelf of the plurality of shelves.
 17. The method of claim 1, wherein positioning a movable portion of the storage apparatus in vertical alignment with a position through which a first wafer carrier supported by the overhead transport mechanism will travel, comprises laterally moving the movable portion relative to the frame.
 18. The method of claim 17, wherein laterally moving the movable portion relative to the frame comprises rotating the movable portion.
 19. The method of claim 18, wherein rotating the movable portion comprises moving the movable portion through an arc.
 20. The method of claim 19, wherein moving the movable portion through an arc comprises moving the movable portion outward of the frame.
 21. The method of claim 20, wherein moving the movable portion outward of the frame comprises moving the movable portion beyond a footprint of the frame.
 22. The method of claim 17, wherein laterally moving the movable portion relative to the frame comprises causing the movable portion to translate relative to the frame.
 23. The method of claim 22, wherein causing the movable portion to translate relative to the frame comprises linearly extending the movable portion.
 24. The method of claim 23, wherein linearly extending the movable portion comprises moving the movable portion outward of the frame.
 25. The method of claim 24, wherein moving the movable portion outward of the frame comprises moving the movable portion beyond a footprint of the frame.
 26. An apparatus for storing and moving wafer carriers, comprising: a frame adapted to be positioned adjacent an overhead transport mechanism adapted to support a plurality of wafer carriers and transport the plurality of wafer carriers along a wafer carrier transport path; at least one shelf supported by the frame and adapted to support and store a wafer carrier; and a movable portion supported by the frame, the movable portion being adapted to extend and retract relative to the frame, so as to contact a wafer carrier supported by the overhead transport mechanism, and so as to remove the wafer carrier from the overhead transport mechanism, such that the movable portion supports the wafer carrier and the adjacent overhead transport mechanism no longer supports the wafer carrier.
 27. The apparatus of claim 26, wherein the frame supports the movable portion such that the movable portion is vertically aligned with the wafer carrier transport path.
 28. The apparatus of claim 26, wherein the frame supports the shelf such that the shelf is vertically aligned with the wafer carrier transport path.
 29. The apparatus of claim 26, wherein the at least one shelf supported by the frame comprises a plurality of shelves.
 30. The apparatus of claim 26, wherein the frame supports the shelf such that the shelf is below the wafer carrier transport path.
 31. The apparatus of claim 26, wherein the movable portion is adapted so as to kinematically couple with the wafer carrier.
 32. The apparatus of claim 26, wherein the movable portion is vertically aligned with the at least one shelf.
 33. The apparatus of claim 26, further comprising a first actuator adapted to extend and retract the movable portion relative to the frame.
 34. The apparatus of claim 33, wherein the first actuator is supported by the frame.
 35. The apparatus of claim 33, wherein the first actuator is adapted to extend and retract the movable portion vertically.
 36. The apparatus of claim 33, wherein the first actuator comprises a portion of a load port assembly.
 37. The apparatus of claim 33, wherein the movable portion is further adapted to extend laterally relative to the frame so as to align with the wafer carrier supported by the overhead transfer mechanism.
 38. The apparatus of claim 37, wherein the movable portion is adapted to extend laterally by rotating through an arc relative to the frame.
 39. The apparatus of claim 37, wherein the movable portion is adapted to extend laterally by moving linearly relative to the frame.
 40. The apparatus of claim 37, wherein the movable portion is adapted to extend laterally beyond a footprint of the frame.
 41. An apparatus for storing and moving wafer carriers, comprising: a frame adapted to be positioned adjacent an overhead transport mechanism adapted to support a plurality of wafer carriers and transport the plurality of wafer carriers along a wafer carrier transport path; a robot supported by the frame and adapted to move wafer carriers relative to the frame; at least one shelf supported by the frame and adapted to support and store a wafer carrier; and a movable portion supported by the frame, the movable portion being adapted to extend and retract relative to the frame, so as to contact a wafer carrier supported by the overhead transport mechanism, and so as to remove the wafer carrier from the overhead transport mechanism, such that the movable portion supports the wafer carrier and the adjacent overhead transport mechanism no longer supports the wafer carrier.
 42. The apparatus of claim 41, wherein the robot is adapted to move wafer carriers onto and off of the at least one shelf.
 43. The apparatus of claim 41, wherein the robot is adapted to move wafer carriers between the at least one shelf and a load port.
 44. The apparatus of claim 41, wherein the robot is adapted to move wafer carriers between the movable portion and the at least one shelf.
 45. The apparatus of claim 41, wherein the robot comprises a vertical guide and a horizontal guide. 